India's ruling Congress party said it cannot spare Prime Minister Manmohan Singh for the post of president, scotching talk of a change in leadership two years ahead of general elections.

Two key supporters of the Congress party - Mamata Banerjee of the Trinamool Congress and Mulayam Singh Yadav of the Samajwadi or Socialist party - proposed Dr Singh's name along with that of Left leader Somnath Chatterjee and former president A.P.J. Kalam as their choice of president on Wednesday evening.

The Congress party yesterday rejected all three names, chiding its close allies for including the name of the premier, who is facing criticism for mishandling the country's economy.

"We have said this umpteen times and I am repeating it again that Dr Manmohan Singh will continue to serve the country as prime minister till 2014 General Elections. He cannot be spared from the prime minister's job. He will stay on the job till 2014," said Congress spokesman Janardan Dwivedi.

The post of president falls vacant next month when India's first female president Pratibha Patil, 77, completes her term.

For the Congress party, the presidential race is shaping up to be a big political test especially as it does not have the numbers to nominate the president on its own. It is dependent on its allies and other friendly parties to gather consensus for a candidate.

Choosing a president is a complex process done through an electoral college, which consists of the votes of 776 Members of Parliament and 4,120 Members of Legislative Assemblies.

The president's post is largely ceremonial but in a time of coalition politics it has assumed importance, with the president having final say on any piece of legislation passed in parliament and during government formation.

The Congress on its own has 31 per cent of the votes while the Congress coalition has 42 per cent. So it needs to get its allies on board and find support from other friendly parties.

Finance Minister Pranab Mukherjee, a seasoned politician known as the party's key troubleshooter, remains the frontrunner for the Congress party nomination, followed closely by Vice-President Hamid Ansari, 77, a former diplomat.

But Congress' two key allies are playing hardball, refusing to support either Mukherjee or Ansari.

The Congress-led government's second term in office has not just been punctuated by corruption scandals and a poor showing in recent polls but also trouble from the Trinamool Congress which has blocked key reforms.

By proposing their own set of candidates, Banerjee and Yadav are playing 'pressure politics' and angling for budgetary concessions and financial aid, said Lucknow-based political analyst Sudhir Panwar.

"I don't think they are serious about wanting change in the prime minister's position," he said. "But they have embarrassed the Prime Minister."